Elastomeric keyboard with improved printed circuit contact means

ABSTRACT

A signal-actuating device having its major component parts molded as a single piece. The actuating device includes a single body composed of an elastomeric material which is a glycol cured isocyanate terminated polyester formulated to be virtually a true gel, character symbols bonded on the body representing key positions and Mylar circuitry strips of etched copper wires bonded to raised projections located on the underside of the body. Contact made by depressing a key gives a binary-coded output, as well as providing a signal for activating distant devices.

United States Fatent Inventor Samuel A. Redman Garden City, N.Y.

Nov. 5, 1969 July 13, 1971 The National Cash Register Company Dayton,Ohio Appl. No. Filed Patented Assignee ELASTOMERIC KEYBOARD WITHIMPROVED PRINTED CIRCUlT CONTACT MEANS 5 Claims, 5 Drawing Figs.

US. Cl 2011/! R, 200/5 E, 200/86 R int. Cl 110111 9/00,

H01h 9/26, H01h 3/02 Field of Search 200/1 A, 1,

References Cited UNITED STATES PATENTS 9/1962 Larson 3,120,583 2/1964Cornell lll 200/5 (E) 3,308,253 3/1967 Krakinowski 200/86 X 3,495,2322/1970 Wagner 200/1 X FORElGN PATENTS 382,831 12/1964 Switzerland 200/86Primary Examiner.l. R. Scott Attorneys-Louis A. Kline, Wilbert Hawk, Jr.and Richard W.

Lavin ABSTRACT: A signal-actuating device having its major componentparts molded as a single piece. The actuating device includes a singlebody composed of an elastomeric material which is a glycol curedisocyanate terminated polyester formulated to be virtually a true gel,character symbols bonded on the body representing key positions andMylar circuitry strips of etched copper wires bonded to raisedprojections located on the underside of the body. Contact made bydepressing a key gives a binary-coded output, as well as providing asignal for activating distant devices.

PATENTED JUL} 3191: 592, 979

sum 1 [1F 2 VENT yw 2W HIS ATTORNEYS ELASTOMERIC KEYBOARD WITH IMPROVEDPRINTED CIRCUIT CONTACT MEANS BACKGROUND OF THE INVENTION Priorkeyboards have been utilized in adding machines, cash registers, andaccounting machines in which each of the keys has been individuallyconstructed and mounted in a framework with attending detent members forcontrolling various mechanisms within the machine. Because of themechanical nature of these keyboards and of the close tolerances thatare required for proper operation, the keyboards are quite bulky indimension and costly to manufacture. This type of keyboard is also proneto mechanical failure due to its complex construction. In order toovercome these disadvantages, it is the object of this invention toprovide a keyboard device which is simple in construction and thereforelow in cost.

SUMMARY OF THE INVENTION A keyboard device includes a single elastomericbody with character symbols bonded on molded keys or key positions onthe body and Mylar circuitry strips of etched copper wires bonded to aseries of cylindrical projections located in rectangular grids formed inthe underside of the body. A circuitry panel of Mylar strips with etchedcopper wires is positioned adjacent to the elastomeric body, with thecopper wires orientated in a direction to form a cross bar switchmechanism with the circuitry strips of the elastomeric body, which, upondepression of the elastomeric body at the key position, will makecontact between the circuitry strips to produce a binarycoded output aswell as providing a signal for actuating distant devices.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 isa partial crosssectional viewof the keyboard.

FIG. 2 is a partial detailed view of the underside of the keyboardshowing the grid patterns and the location-of the circuitry strips.

FIG. 3 is a diagrammatic view of an L-shaped key and its relationshipwith the cylindrical projections.

FIG. 4 is a diagrammatic view of the cross bar circuitry for the key ofFIG. 3 showing the contact points between the copper wires.

FIG. 5 is a detailed sectional side view of the molding die used to formthe elastomeric keyboard member.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, thereis shown a partial sectional view of the keyboard which includes themain body composed of an elastomeric material. An example of thematerial that can be utilized is a liquid polyurethane system whichconsists of an isocyanate terminated polyester liquid polymer cured witha glycol curative, such as trimethanol propane. This stoichiometriclevel provides a degree of chain lengthening action with thecross-linking mechanism, so as to produce a polymer structure which canbe regarded as a true gel. As such, this polymer has an extremely highcoefficient of restitution. When the material is depressed or placedinto any sort of flexure and then released, it assumes its originalposition in a very short period of time. Thus, the use of this materialin the device to be disclosed is very important, since it permits theinstantaneous springback which is so necessary in any type of keyboardor device into which a digital input is made.

As shown in FIG. 2, the bottom portion of the elastomeric body 20 iscomposed of a grid 21 design with a circular fingerlike cylindricalmember 22 located centrally in each of these grids. The walls 23 of eachof the grids 21 provide a floating effect for each of the cylindricalmembers 22. Each of the members 22 is positioned opposite a charactersymbol 24 (FIG. I), which is composed of a printed polyester filmMartino... M a al-win u/Phhino which in turn is molded on of each of themembers 22 tends to separate one character.

symbol from another, so that, as a single depression is' made, no matterhow forceful, it would not in turn cause other members 22 injuxtaposition to be depressed.

Bonded to the underside of the body 20 and extending in a lengthwisedirection along each row of the cylindrical members 22 is a strip 25(FIG. 1), of Mylar, in which are embedded a plurality of copper wires 26(FIGS. 2 and 4). As shown in FIG. 2, the strip 25 is somewhat narrowerthan the grids 21 and follows the contours (FIG. 1) of the gridstructure and is bonded directly to each of the members 22.

The second part of the keyboard is a bottom circuit strip 27 (FIG. 1),which is similar in construction to the strip 25 and I which strip 27 isadhesively attached to a plastic plate 28,

which in turn is molded as part of the cabinetry of the machine or isbonded to the cabinetry 30 of the machine if so constructed. This strip27, of Mylar, also contains wires of copper 31 (FIGS. 1 and 4), whichrun perpendicular to the wires of copper 26 (FIG. 4). Both sets ofcopper wires 26, 31 constitute a cross bar switching mechanism. As shownin FIG. 4, selected areas of the Mylar strips are cut away, exposingadjacent copper wires. These contacts points are designated as 32. Witha source of voltage applied to the copper wires, depression of anycharacter on the keyboard would result in the engagement of selectivecopper wires 26, 31 at contact points 32, resulting in a number ofsingle voltages being generated. Since each character on the keyboardwould have a different number of contacts 32, a binary-coded outputcould be generated. For example, if each of the Mylar strips 25, 27contained eight copper wires, the total number of characters that couldbe accommodated would be as high as 500 or more. An electronic timedelay is required from the moment of initial contact until registrationof the impulses to insure that all contacts required by a given key aremade. The elastomeric cylindrical members 22 will insure intimacy ofcontact between the adjacent copper wires, but, no matter how delicatelyor forcefully a key is depressed, in a situation where multiple contactsare made to produce a given code or signal, there will always be asuccession of these contacts, separated, of course, from each other byonly milliseconds. In an actual keying situation, this would produce afalse input. A momentary time delay of, for example, 20 millisecondsbefore registration willprevent this fast keying. The signal of thefirst contact can be designed to activate the time delay mechanism.

In some keyboards, it may be desirable to have some keys larger thanothers because they are more frequently used, such as zero or tabulatingbar. Such a key 33 (FIG. 3) may be represented as an L-shaped membertraversing the entire bottom of the keyboard and cover a number ofcharacter positions. All that is required is that there be no wallsseparating the members 22 under the keys from each other. FIG. 4 shows aportion of the copper strip wiring for such a key arrangement.

Referring now to FIG. 5, there is shown a schematic representation ofthe molding die used to mold the elastomeric body 20. The charactersymbols 24, as previously disclosed, are prefabricated on a fabricwebbing 40 and are made of a printed polyester film. This webbing isplaced by means of locating pins (not shown) mounted on the upper dieplate 34. On a lower die plate 35 are positioned the Mylar circuitrystrips 25, loaded just prior to fitting the die plates together. Thecomponents of the polyurethane system are mixed and loaded into a pot 36through the pipe 41. A ram 37 is operated to push downward into the pot36, forcing the liquid material through the channel 38 into the maincavity, filling all impressions and, under pressure, contacting both thecharacter symbols 24 and the circuitry strips 25, which have beenprecoated with a thin layer of urethane adhesive such as DaytonChemicals, Thixom 1153 or Hughson Chemical, Chemlok 2l8. After thecuring cycle, the finished part is ejected and can be held andmanipulated as a single item. Post cure of 16 hours at 212 F. isrequired to achieve optimum properties.

If desired, the die can be designed to produce a panel with raised keyseven to the point of simulating the style of the conventional keyboard,with each key rectangular and standing seemingly alone separated fromthe adjacent key by a thin moat produced by knifelike projections fromthe upper plate 34 of the molding die.

Instead of the copper wires described previously, pressuresensitivetransducers or diodes could be incorporated. Other forms of pressureswitches, such as a reticulated form contain ing conductive slivers orfilings, might be utilized to produce electrical contact.

The keyboard as it comes from the molding die and after post cure isready for assembly into the machine. Wire attachments are made bysoldering directly to the copper wires. in place, the keyboard isoperated as any conventional mechanical keyboard, the operatordepressing the key desired designated by the character symbol untilcontact is felt or registration is in some way signaled. With the typeof elastomer used for the keyboard, keying is accomplished very rapidly.Restoration is accomplished almost instantaneously when the operatorsfinger is released, and one can move on to subsequent keys withouthesitation.

What I claim is:

l. A keyboard device for generating binary information including:

a. a deformable body composed of an clastomeric material having a smoothupper surface and a plurality of rows of grid portions formed on itslower surface, each grid portion containing a portion of the body formedas a protrusion extending from the body;

b. a plurality of first parallel strips of insulating material bonded tothe lower surface of the body, each strip extending along a row of gridportions and positioned on the lower surface of the protrusions locatedin each of the grid portions, said strips having selected openingstherein;

c. a plurality of conductive contact elements embedded in each of saidstrips of insulating material, portions of which contact elements arelocated in said openings;

d. an indicia-bearing fabric sheet bonded to the top surface of thedeformable body, the indicia being aligned with the protrusions on thelower surface ofthe deformable body;

. a support member mounted adjacent the lower surface of said deformablebody; f. a plurality of second parallel strips of insulating materialattached to said support member, each of said second strips containingopenings therein and a plurality of conductive contact elements havingportions located in said openings, said second Strips being orientatedat right angles with said first strips;

g. and means connected to each of the contact elements in said first andsecond strips for generating electrical signals whereby, upon depressionof an indicia-bearing portion of the deformable body, contact is madebetween selected contact elements located in adjacent openings in saidfirst and second insulation strips to produce a predetermined binaryoutput signal.

2. The keyboard device of claim 1 in which said protrusions constitute acylindrical body.

3. The keyboard device of claim 2 in which formed wall portionsconstitute said grid portions within which the cylindrical body iscentered, whereby depression on the deformable body adjacent acylindrical body will not affect adjacent cylindrical bodies.

4. A keyboard device including a. deformable body composed of anelastomeric material with a smooth upper surface having a plurality ofindicia thereon and a lower surface formed in a grid pattern with hillsand valleys and a raised portion located within each grid, each of saidraised portions being orientated opposite one ofsaid indicia',

b. a first strip of insulating material bonded to the lower surface ofeach of said raised portions, said strip containing a plurality ofselectively positioned apertures and a plurality of conductive contactelements embedded therein, said contact elements having portions locatedwithin said apertures;

c. and a second strip of insulating material having the sameconstruction as said first strip, said second strip being positionedadjacent said raised portions and orientated at right angles to saidfirst strip, whereby, upon depression of an indicia-orientated portionof said deformable body, selective portions of conductive contactelements in said first and second strips will be brought into contactwith each other by the raised portion orientated with the depressedindicia.

5. The keyboard device of claim 4 in which said raised portion comprisesa cylindrical body.

2. The keyboard device of claim 1 in which said protrusions constitute acylindrical body.
 3. The keyboard device of claim 2 in which formed wallportions constitute said grid portions within which the cylindrical bodyis centered, whereby depression on the deformable body adjacent acylindrical body will not affect adjacent cylindrical bodies.
 4. Akeyboard device including a. deformable body composed of an elastomericmaterial with a smooth upper surface having a plurality of indiciathereon and a lower surface formed in a grid pattern with hills andvalleys and a raised portion located within each grid, each of saidraised portions being orientated opposite one of said indicia; b. afirst strip of insulating material bonded to the lower surface of eachof said raised portions, said strip containing a plurality ofselectively positioned apertures and a plurality of conductive contactelements embedded therein, said contact elements having portions locatedwithin said apertures; c. and a second strip of insulating materialhaving the same construction as said first strip, said second stripbeing positioned adjacent said raised portions and orientated at rightangles to said first strip, whereby, upon depression of anindicia-orientated portion of said deformable body, selective portionsof conductive contact elements in said first and second strips will bebrought into contact with each other by the raised portion orientatedwith the depressed indicia.
 5. The keyboard device of claim 4 in whichsaid raised portion comprises a cylindrical body.